The sockets for domestic and commercial electricity are generally categorized into types utilized in 110-120V or 220-240V. The 110V-120V socket is further divided into a two-hole type and a three-hole type. Therefore, the type of the sockets has to be chosen in advance before installing or purchasing sockets. For example, the three-hole type sockets utilized to 220-240V should be installed nearby where the air-conditioner will be set, and the two-hope type or the three-hole type sockets utilized in 110-120V should be installed nearby where the electronic appliances will be set. In addition, not only should the voltage should be considered, the types of sockets should be noted as well in case, for example, the three-pin plug will not fit the two-hole sockets. Furthermore, the plugs have to be inserted in specific direction, in this situation, the power cable will be curved and the insulation layer of the power cable may rupture, resulting in leakage of electricity or a short circuit.
The electronic appliances which are purchased overseas cannot be used anymore since the sockets do not fit the plugs. Although there are adapters available on the markets, however, it's inconvenient to attach an adapter on the plug, and occupy more space and sometimes cause danger due to the low-quality of the adapters.
Furthermore, the Power Line Communication (PLC) technologies allow the network data to be transmitted by the power cables. The PLC technologies requires modems installed on sockets or network bridge with PLC functions, however it's inconvenient to attach an adapter on the plug, and occupy more space as well.